1. Field of the Invention
The present invention relates to a α-L-iduronidase knock-out mouse. More particularly, this invention relates to a α-L-iduronidase knock-out mouse to be designed for developing a treatment or an agent for mucopolysaccharidosis type I (Hurler syndrome or Hurler-Scheie syndrome) as an animal model.
2. Description of Prior Art
Mucopolysaccharidosis is a metabolic disorder caused by the absence or mal-function of lysosomal enzyme required for degenerating the glycosaminoglycan, one of long chain of sugar carbohydrates in the cell, which helps to build the bone, cartilage, tendon, cornea, skin and connective tissue.
Mucopolysaccharidosis (MPS) I can be classified into three sub-types based on severity of symptom. All three types result from the absent or insufficient levels of α-L-iduronidase enzyme (IDUA; mucopolysaccharide α-L-idurono-hydrolase; EC 3.2.1.76). Iduronidase is an enzyme involved in the degeneration of glycosaminoglycans, such as, dermatan sulfate and heparan sulfate, which are found in the lysosome in the cell. The defective α-L-iduronidase results in the accumulation of heparin and dermatin sulfate within phagocytes, endothelium, smooth muscle cells, neurons, and fibroblasts.
MPS I H is also called as Hurler syndrome, and it is the most severe syndrome of the MPS I sub-types. Delay of development is obvious by the end of the first year, and patient usually stops developing between ages 2 and 4. Further, progressive mental decline and loss of physical skills follow. Growth in height may be faster than normal, but begins to slow before the end of the first year. Then, the growth often ends around age 3.
MPS I S is also called as Scheie syndrome, and it is the mildest form of MPS I. Symptoms generally begin to appear after age 5, and diagnosis of this symptom can be made after age 10. Even though some of children having Scheie syndrome shows normal intelligence, others may have a mild learning disability and a psychiatric problem. The symptoms such as glaucoma, retinal degeneration, or clouded corneas may impair the vision of child.
MPS I H-S is also called as Hurler-Scheie syndrome, and it is less severe than Hurler syndrome. Symptoms generally begin between ages 3 and 8. Children may have moderate mental retardation and learning disability. Skeletal and systemic irregularities include short stature, marked smallness in the jaws, progressive joint stiffness, compressed spinal cord, clouded corneas, hearing loss, heart disease, coarse facial features, and umbilical hernia. Respiratory problems, sleep apnea, and heart disease may develop in adolescence.
To develop the agent for treating MPS I, knock-in mouse model for developing the agent has been designed. In U.S. Pat. No. 6,002,067, knock-in mouse which is homozygous for a disruption in the IDUA gene, but which has normal expression for the SAT-1 gene has been disclosed. In this disclosure, it has been also disclosed that knock-in mouse can be used for evaluating therapeutic agents in treating mucopolysaccharidosis Type I, by administering the therapeutic agent to the mouse, and evaluating the mouse for tissue pathology associated with iduronidase deficiency.
However, it has a doubt if knock-in mouse is the best model for evaluating the ability of a targeting system to deliver a therapeutic agent to selected tissues or organs by administering an effective iduronidase replacement therapy, because knock-in mouse has a possibility to show different pathophysiological characteristics of human iduronidase deficiency syndrome, such as, Hurler syndrome or Hurler-Scheie syndrome.
For treating a mucopolysaccharidosis (MPS) I, Genzyme Co., Ltd. has developed the enzyme of α-L-iduronidase as trademark of ‘Aldurazyme’ using CHO cell by genetic engineering method. In 2003, this enzyme drug has been approved for treating Hurler syndrome or Hurler-Scheie syndrome by FDA. Recently, this drug has been commercially marketed in about 20 countries.
Aldurazyme consists of 653 amino acids. In this enzyme, there are 6 N-linked oligosaccharide sites which are 110th residue, 190th residue, 336th residue, 372nd residue, 415th residue and 451st residue. Further, mannose 6-phosphate chain has been linked to 336th residue and 451st residue. Intracellular absorption of this enzyme has been made by the affinity between mannose 6-phosphate chain and mannose 6-phosphate receptor in the cell. Like other enzyme prepared by recombinant DNA method, Aldurazyme also has a handicap of absorption in the cells of patient.
Direct enzyme replacement method has been developed for administrating an Aldurazyme or its analogue for treating Hurler syndrome or Hurler-Scheie syndrome. Further, cell implant or gene therapy using vector also have been tried for treating Hurler syndrome or Hurler-Scheie syndrome. Any of treating methods developed until now cannot show the sufficient treating effect. Further, we cannot estimate which treating method will be effective to individual patient.
The present invention is to provide a knock-out mouse model for diagnosing or treating Hurler syndrome or Hurler-Scheie syndrome. For this purpose, the inventor has prepared α-L-iduronidase knock-out mouse, in which wild type of α-L-iduronidase gene has been replaced by knock-out targeted gene.